Extensive studies have been made on a so-called ink jet recording apparatus which provides recording on a paper, cloth, film or the like by discharging a liquid or molten solid ink through a nozzle, slit or porous film taking into account its advantages such as small size, cheapness and low noise. In particular, a printer which can provide a good printing quality on a so-called plain paper such as reporting pad paper and copying paper is commercially available as a black monochromic printer.
An ink for use in thermal ink jet recording apparatus has the following requirements:
(1) causes no corrosion or decomposition of the print head material;
(2) causes no deposition of materials constituting the ink, particularly dyes in the case of a dye-containing ink, when stored for a prolonged period of time;
(3) causes no clogging in the tip of the print head;
(4) causes little scorching on the heater called kogation; and
(5) causes no hue unevenness, blank area and disturbance in the practically printed recorded image. In particular, the requirement (4) is an important assignment and has heretofore been extensively studied.
JP-A-3-160070 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") discloses an approach which comprises the addition of an oxo anion. JP-B-3-48953 (the term "JP-B" as used herein means an "examined Japanese patent publication") discloses an approach which comprises limiting the content of metallic impurities. JP-A-4-227669 discloses an approach which comprises the addition of an organic sulfonate to minimize kogation.
Although the foregoing approaches provide some reduction of kogation, none of these approaches can satisfactorily meet all these requirements.
It is therefore an object of the present invention to provide an ink for thermal ink jet recording which minimizes kogation on the heater, causes no corrosion or decomposition of the heat material, exhibits a high coloring material dissolution stability during prolonged storage or use and causes no clogging or emission unevenness.
The foregoing object of the present invention will become more apparent from the following detailed description and examples.
The inventors found that an ink for thermal ink jet recording comprising water and a coloring material as essential components, which contains an amino compound having three hydroxyl groups in one alkyl side chain, minimizes kogation on the heater, causes no corrosion or decomposition of the heat material, exhibits a high coloring material dissolution stability during prolonged storage or use and causes no clogging or jetting unevenness. Thus, the present invention was worked out.
The foregoing object of the present invention is accomplished with an ink for thermal ink jet recording comprising water, a coloring material and an amino compound represented by formula (I) or (II): ##STR2## wherein R.sub.1 represents a C.sub.1-5 alkyl group having a hydroxyl group; R.sub.2, R.sub.7 and R.sub.8 may be the same or different and each represents a hydrogen atom or a C.sub.1-5 alkyl group having a hydroxyl group; R.sub.3, R.sub.4 and R.sub.5 may be the same or different and each represents a C.sub.1-3 alkylene group; and R.sub.6 represents a C.sub.1-5 alkylene group.